ARB RD149 - Manual (Page 13)

3 Installing the Air Locker
11
3.3 Drilling and Tapping the Bulkhead Port
An air line port must be drilled and tapped through the differential
housing to mount the bulkhead fitting into.
Mark a spot on the top of the outside of the differential housing that
will be clear of the ring gear position once the seal housing tube
has been installed. (Fig.6.)
NOTE : Higher ratio gearing uses deeper (thicker) ring gears
with teeth that extend much further. Make sure the
intended hole location is far enough away from the
ring gear teeth that the air line will not be at risk of
contact with the current or future ring gears.
Figure 6.
Cover the drive pinion and axle tube areas with a rag to protect
them from metal filings.
Drill an 11.2mm [7/16”] diameter hole through the differential
housing square to the outside surface.
Tap the hole from the outside using ¼”NPT thread tap.
Remove any sharp edges that may chip off from around the hole
and fall into the housing.
Very carefully, remove the rags and inspect with a service light
inside the housing to ensure no metal filings are left behind.